“Hydraulic fracturing” is a common and well-known enhancement method for stimulating the production of natural gas. The process involves injecting fluid down a well bore at high pressure. The fracturing fluid is typically a mixture of water and proppant (the term “proppant” includes sand and synthetics). Other chemicals are often added to the proppant to aid in proppant transport, friction reduction, wettability, pH control and bacterial control.
Varying amounts of water are required in a typical hydraulic fracturing operation. Water is usually trucked to the well head site from other locations, typically in large quantities. The water may come from a variety of sources that include untreated water from rivers, lakes, or water wells. Once delivered to the well head site, the water is mixed with the proppant particulates and then pumped down the well bore.
During the fracturing process, the fracturing fluid penetrates producing formations (sometimes called “subterranean formations”) at sufficient hydraulic pressure to create (or enhance) underground cracks or fractures—with the proppant particulates supporting the fracture for “flow back.” Sometimes the process is repeated a multiple number of times at the well site. When this is done, the well head is closed between stages to maintain water pressure of the fracturing fluid for a period of time.
The process creates a significant amount of fluid “flow back” from the producing formation. Untreated flow back often is not recyclable in subsequent fracturing operations because of the contaminants it contains. Flow back is normally hauled away and treated off-site relative to the geographic location of the well head.
Hydraulic fracturing is very important to companies involved in the production of natural gas. These companies have made large investments in looking for ways to improve upon all phases of the fracturing operation. One obvious drawback to fracturing involves the high cost of hauling water to the well head site followed by retrieving and hauling away the flow back by-product for off-site treatment and subsequent disposal.
There have been many attempts at improving gas production that results from fracturing operations by varying the make-up and use of the fracturing fluid. Attempts at stimulating natural gas production via fracturing generally falls in two categories: hydraulic fracturing and “matrix” treatments.
Fracturing treatments stimulate gas production by creating more flow paths or pathways for natural gas to travel up the well bore for retrieval. Matrix treatments are different in that they are intended to restore natural permeability of the underground formation following damage. The make-up of the fracturing fluid is often designed to address different situations of this kind by making adjustments in the material and chemical content of the fluid and proppant particulates.
The methods and processes disclosed here involve the quality of the water used to make up the fracturing fluid and treatment of flow back and other water-based fluids produced from hydraulic fracturing or other source waters for gas retrieval operations. There are many advantages to the methods disclosed here: First, the disclosed methods provide a means for significantly reducing trucking costs to and from the well head site that directly relate to the large quantities of water typically needed for hydraulic fracturing. Second, the disclosed methods offer a viable way to recycle the water used as the fracturing fluid in an energy efficient treatment process at the well head site. Third, because of the nature of the treatment process, for reasons explained below, the delivered or recycled water component in the fracturing fluid improves flow back and increases the quantity of natural gas produced that results from the fracturing operation.
In sum, the methods and processes disclosed below serve to improve natural gas production at a lower water treatment cost.